During the construction or repair of an electrical panel or junction box and the like it is necessary for the electrician to remove the cover or door to the unit for extended periods of time. A temporary cover is very useful and necessary for safety when the unit needs to be left unattended. Often an electrician will leave panels exposed or may resort to applying a piece of cardboard or similar material with tape to serve this purpose. Usually, this type of temporary, makeshift cover does not convey the potential safety hazard and may not adhere adequately to the unit for extended periods of time. This approach would not meet federal safety standards.
Temporary protective covers for switches and outlets have been disclosed (U.S. Pat. No. Des. 307,538; U.S. Pat. No. Des. 345,142; U.S. Pat. No. 4,907,711; and U.S. Pat. No. 5,003,128). These covers do not use magnetic adhering means nor are they practically adaptable for large electrical panels. On the other hand, signs with magnetic adhering means have been disclosed (U.S. Pat. Nos. 2,957,261 and 3,372,503). These magnetic signs require a large number of small magnets or magnetic strips that occur at no greater intervals than 3 inches throughout the area of the sign. A large number of small magnets offer the disadvantages of high cost and complexity of manufacturing compared to magnetic strips. On the other hand, the use of numerous magnetic strips places said strips within the central area of the sign. In the case of the electrical covers, magnetic strips in the central area of the cover would not be useful because there would be no surface for adherence. In addition, placing electrically conducting magnetic strips in proximity to electrical parts is unwanted and unsafe. Thus, with electrical panel covers the magnets must be confined to the edges of the cover, still provide sufficient force for adherence, and, for safety, must not be electrically conducting.
The difficulties in creating a cover with magnetic adhering means for an electrical panel are that the cover has to be strong and durable and the magnets, being functionally restricted to the edges of the cover, have to provide sufficient magnetic force to prevent the sign from slipping or from being readily dislodged. Thus, the relationship between the weight of the cover and the adhering force of the magnets must be such that the cover will be held firmly in place. Furthermore, for safety reasons, the magnetic adhering means must be electrically non-conducting. Since critical features of the cover are that it have some rigidity in three dimensions and resist penetration with reasonable use, it is essential that the cover be constructed of sufficiently strong durable materials. The mass and density of standard materials disclosed in the prior art for these signs require an extensive amount of magnets. Construction of electric panel covers similar to that described for signs would make the covers expensive, heavy, and inconvenient to transport or store. Also, present industrial safety standards require temporary electrical panel covers to be composed of at least two layers, unlike signs disclosed in the prior art which are only one layer.